IP Address Migration

[Wazzer]

We are required to migrate our entire network to a different IP range in the next couple of weeks. We currently have 2 Windows 2003 Domain Controllers (lets call them DC1 and DC2), each running DNS, DHCP and are both Global Catalogs.
We have 300 PCs. My initial thoughts on how to migrate are:

1) Visit all the PCs and allocate them static addresses in a temporary range on the new IP range. Then do an IP sweep to ensure we haven't missed any. (This is to take DHCP out of the game during the migration so you know where you are.)
2) Disable DHCP on DC2.
3) Alter the IP address on DC2 to the new range
4) Check DNS/ Replication is updating between the two.
5) Disable DHCP on DC1.
6) Alter the IP address on DC1 to the new range
7) Ensure all is working ok.
8) Enable DHCP on new range.
9) Revisit PCs and make them DHCP enabled
10) Perform another IP sweep of the temporary range to ensure all PCs are visited.

This is a simplified list of the plan. My worry is with Domain Controller Replication/ DNS replication between DC1 and DC2 once the IP address is changed on DC2. Am I likely to hit any problems? Any help you can offer is much appreciated.

 

[wallst32]

Visiting each PC to assign static and change back to dynamic sounds like overkill.

In prepartion, I would just set the DHCP lease times to very short time, say 30 minutes.

Then when the time comes, move all the servers to the new address space and update the DNS and DHCP services appropriately. Validate AD is replicating properly. All the client PCs will broadcast for a new DHCP address within 30 minutes, and will connect to the DHCP on the new address space.

 

[58sniper]

I'm with wallst32. Cut the lease time to 30 minutes. This will cause them to renew every 15 minutes (IIRC). Make sure you do that at least one full interval before the change. For example, if your current lease interval is 8 days, make this change at least 9 days before the change. Otherwise, you'll end up with machines that won't request a renewal or new address until after the change. I hope that makes sense.

Create the new scope but don't activate it. Set the lease duration time to your normal desired time.

On "move day",

Disable the existing DHCP scope
Change your IP addresses on your servers, routers, firewalls and other statically assigned devices. Configure the servers for the new DNS servers. On the servers, do an
ipconfig /flushdns
and then an
ipconfig /registerdns
to update the host records in DNS

Enable the new scope.

Verify connectivity. Within 30 minutes, your machines should be connected.

Relish in your brilliance for having saved the rest of the weekend for yourself!

Pat Richard
Microsoft Exchange MVP